Fluid life of a metal can be described in terms of ease and time frame in which the metal can flow through various passages it needs to pass through before it is put into the cast, and how easily it takes up the shape and characteristics of the cast. A molten metal is said to have more fluid life than its capability to take the final shape as o the cast.
In more precise terms, fluid life of an alloy can be seen as the LIQUID property of the metal. Fluid life is much more than what is traditionally described as FLUIDITY of the metal. Fluidity of molten metal gets altered at each step starting from when it is put in a pouring ladle to be put into the cast after passing through die casting chamber, gating system etc. while undergoing this process, molten metal begins to cool and an oxide sheet begins to form on the surface of the metal. As a result, the fluidity of the molten metal lessens, both due to the cooling process and more so due to the formation of oxide sheet.
The temperature of any molten metal cannot in isolation reflect its fluidity. For example aluminum's fluid life is brilliant at 650-750C whereas molten steel cant match the same fluid life even at 1650C. Therefore, it can safely be said that the fluid life of any alloy will depend on factors like the compositional make up, chemical properties and surface tension of the alloy.
The intended design properties of any cast will again depend on the fluid life of any alloy. Studying the fluid life of any alloy will reveal and suggest a number of important tips towards drawing up the design of the cast. Such tips include:-
- Minimum thickness that can be achieved for each section.
- The upper limit of length that any subdivision can attain.
- The level of superiority of surface detail that can possibly be achieved.
However, it should be kept in mind that alloys which have lesser fluid life, to the degree that the fluid life is reasonable or even poor, it will not necessarily reflect on the cost make up of the design. If it is known that the fluid life of an alloy is limited or poor, the design for the cast should be drawn to have:-
- Blunt shapes or shapes with less sharp dimensions.
- Larger number of features at the lower section of the cast rather than on the upper portion.
- Conical structures which taper into thinner endings.
- Bigger inscriptions.
Some processes use casts that are very hot or very dry. These processes serve to minimize the fluid life of the alloy by reducing the impact of convection, which is a mode of producing heat for heat transfer. Some alloys are composed and made up in such a way so as to achieve maximum fluid life. An example of this is 365 aluminum. In this alloy, silicon atoms are present whose heating capability is high. Thus as the fluid life of aluminum decreases, the silicon atoms stimulate the aluminum atoms again and thus increase the fluid life.